Effect of Al on characterization and properties of AlxCoCrFeNi high entropy alloy prepared via electro-deoxidization of the metal oxides and vacuum hot pressing sintering process

AlxCoCrFeNi high-entropy alloys with different Al contents (x in molar ratio, x = 0 - 2.0) were prepared by electrochemical process using the mixed metal oxides as the precursor. The effects of Al addition on the crystal structure, microstructure, mechanical property and corrosion behavior were investigated by XRD, XPS, SEM, FE-EPMA, universal tensile testing machine, Vickers hardness tester and electrochemical workstation. With the increase of Al contents, the crystal structure of AlxCoCrFeNi HEAs transformed from FCC to the mixed crystal structures of FCC and BCC, finally, to BCC + B2. The sigma-phase was formed in AlxCoCrFeNi (x = 0.8 - 1.5) HEA5 during the electrolysis deoxidization. The bulk HEA5 could be prepared successfully via vacuum hot pressing sintering process. The bulk HEA5 exhibit excellent ultimate tensile strength (UTS) and hardness. The hardness of the Al-o (245.2 HV) HEA and Al-0.3 (261.2 HV) HEA was twice high of the sample prepared by arc-melting method. Compared with 304 stainless steel (304SS) and AlxCoCrFeNi HEAs prepared by other method, AlxCoCrFeNi HEAs prepared by the united process shows a comparable corrosion resistance in acid, alkali and salt aqueous solutions. (C) 2021 Published by Elsevier B.V.

Automated summary

AlxCoCrFeNi high-entropy alloys with varying Al content were prepared using an electrochemical process, and the effects of Al addition on crystal structure, mechanical properties, and corrosion behavior were investigated. Increasing Al content led to a transformation in crystal structure and significantly improved hardness and ultimate tensile strength. AlxCoCrFeNi HEAs prepared by the united process showed comparable corrosion resistance to 304 stainless steel and HEAs prepared by other methods.